The present invention relates to a computer system and control technique of it, and in particular to a technique for controlling copying of data among storage areas of storage sub systems by means of a secondary computer belonging to a computer system.
In recent years, in computer systems comprising a host computer and a storage sub system for storing data, it has become common practice to use remote copy technology in order to improve data reliability. Remote copy technology is a technology whereby a multiplicity of storage sub systems are set up within a computer system, with data stored in a storage area in one storage sub system being copied to a storage area in another storage sub system. According to this remote copy technology, even in the event that a malfunction occurs in one storage sub system rendering it inoperable, the computer system can nevertheless continue to carry out tasks using data held in another storage sub system.
Another technique for improving reliability of data in computer systems is to sequentially link a multitude of storage sub systems to a host computer, and perform remote copying of data to the sequentially linked storage sub systems in order to increase data multiplicity (redundancy), so as to enhance data reliability (e.g. JP2000-293674A).
Copying of data within a computer system is typically carried out by defining a copy pair composed of two storage areas, and copying data from one storage area of the copy pair to the other storage area. Where data is copied within a single storage sub system, the copy pair will be composed of two storage areas belonging to one storage sub system. Where remote copying is to be performed, the copy pair will be composed of two storage areas belonging to two different storage sub systems. Information relating to such copy pairs is generally generated and held by the host computer.